NAME
Astro::Sunrise - Perl extension for computing the sunrise/sunset on a
given day
SYNOPSIS
use Astro::Sunrise;
($sunrise, $sunset) = sunrise(YYYY,MM,DD,longitude,latitude,Time Zone,DST);
($sunrise, $sunset) = sunrise(YYYY,MM,DD,longitude,latitude,Time Zone,DST,ALT);
($sunrise, $sunset) = sunrise(YYYY,MM,DD,longitude,latitude,Time Zone,DST,ALT,inter);
$sunrise = sun_rise(longitude,latitude);
$sunset = sun_set(longitude,latitude);
$sunrise = sun_rise(longitude,latitude,ALT);
$sunset = sun_set(longitude,latitude,ALT);
$sunrise = sun_rise(longitude,latitude,ALT,day_offset);
$sunset = sun_set(longitude,latitude,ALT,day_offset);
DESCRIPTION
This module will return the sunrise/sunset for a given day.
Eastern longitude is entered as a positive number
Western longitude is entered as a negative number
Northern latitude is entered as a positive number
Southern latitude is entered as a negative number
inter is set to either 0 or 1. If set to 0 no Iteration will occur. If
set to 1 Iteration will occur. Default is 0.
There are a number of sun altitides to chose from. The default is -0.833
because this is what most countries use. Feel free to specify it if you
need to. Here is the list of values to specify altitude (ALT) with:
0 degrees
Center of Sun's disk touches a mathematical horizon
-0.25 degrees
Sun's upper limb touches a mathematical horizon
-0.583 degrees
Center of Sun's disk touches the horizon; atmospheric refraction
accounted for
-0.833 degrees
Sun's supper limb touches the horizon; atmospheric refraction
accounted for
-6 degrees
Civil twilight (one can no longer read outside without artificial
illumination)
-12 degrees
Nautical twilight (navigation using a sea horizon no longer
possible)
-15 degrees
Amateur astronomical twilight (the sky is dark enough for most
astronomical observations)
-18 degrees
Astronomical twilight (the sky is completely dark)
USAGE
sunrise
"($sunrise, $sunset) = sunrise(YYYY,MM,DD,longitude,latitude,Time
Zone,DST);"
"($sunrise, $sunset) = sunrise(YYYY,MM,DD,longitude,latitude,Time
Zone,DST,ALT);"
Returns the sunrise and sunset times, in HH:MM format. (Note:
Time Zone is the offset from GMT and DST is daylight savings
time, 1 means DST is in effect and 0 is not). In the first form,
a default altitude of -.0833 is used. In the second form, the
altitude is specified as the last argument. Note that adding 1
to the Time Zone during DST and specifying DST as 0 is the same
as indicating the Time Zone correctly and specifying DST as 1.
Notes on Iteration
($sunrise, $sunset) = sunrise(YYYY,MM,DD,longitude,latitude,Time
Zone,DST,ALT,inter);
The orginal method only gives an approximate value of the
Sun's rise/set times. The error rarely exceeds one or two
minutes, but at high latitudes, when the Midnight Sun soon
will start or just has ended, the errors may be much larger.
If you want higher accuracy, you must then use the iteration
feature. This feature is new as of version 0.7. Here is what
I have tried to accomplish with this.
a) Compute sunrise or sunset as always, with one exception:
to convert LHA from degrees to hours, divide by 15.04107
instead of 15.0 (this accounts for the difference between
the solar day and the sidereal day.
b) Re-do the computation but compute the Sun's RA and Decl,
and also GMST0, for the moment of sunrise or sunset last
computed.
c) Iterate b) until the computed sunrise or sunset no longer
changes significantly. Usually 2 iterations are enough, in
rare cases 3 or 4 iterations may be needed.
*For Example*
($sunrise, $sunset) = sunrise( 2001, 3, 10, 17.384, 98.625, -5, 0 );
($sunrise, $sunset) = sunrise( 2002, 10, 14, -105.181, 41.324, -7, 1, -18);
($sunrise, $sunset) = sunrise( 2002, 10, 14, -105.181, 41.324, -7, 1, -18, 1);
=back
sun_rise
"$sun_rise = sun_rise( longitude, latitude );"
"$sun_rise = sun_rise( longitude, latitude, ALT );"
"$sun_rise = sun_rise( longitude, latitude, ALT, day_offset
);"
Returns the sun rise time for the given location. The
first form uses today's date (from Time::Object) and the
default altitude. The second form adds specifying a
custom altitude. The third form allows for specifying an
integer day offset from today, either positive or
negative.
*For Example*
$sunrise = sun_rise( -105.181, 41.324 );
$sunrise = sun_rise( -105.181, 41.324, -15 );
$sunrise = sun_rise( -105.181, 41.324, -12, +3 );
$sunrise = sun_rise( -105.181, 41.324, undef, -12);
sun_set
"$sun_set = sun_set( longitude, latitude );"
"$sun_set = sun_set( longitude, latitude, ALT );"
"$sun_set = sun_set( longitude, latitude, ALT, day_offset
);"
Returns the sun set time for the given location. The
first form uses today's date (from Time::Object) and the
default altitude. The second form adds specifying a
custom altitude. The third form allows for specifying an
integer day offset from today, either positive or
negative.
*For Example*
$sunrise = sun_set( -105.181, 41.324 );
$sunrise = sun_set( -105.181, 41.324, -15 );
$sunrise = sun_set( -105.181, 41.324, -12, +3 );
$sunrise = sun_set( -105.181, 41.324, undef, -12);
AUTHOR
Ron Hill rkhill@firstlight.net
SPECIAL THANKS
Robert Creager [Astro-Sunrise@LogicalChaos.org] For providing
help with converting Paul's C code to perl For providing code
for sun_rise, sun_set sub's Also adding options for different
altitudes.
Joshua Hoblitt [jhoblitt@ifa.hawaii.edu]
For providing the patch to convert to DateTime
CREDITS
Paul Schlyer, Stockholm, Sweden
for his excellent web page on the subject.
Rich Bowen (rbowen@rbowen.com)
for suggestions
Adrian Blockley [adrian.blockley@environ.wa.gov.au]
for finding a bug in the conversion to local time
Lightly verified against
http://aa.usno.navy.mil/data/docs/RS_OneYear.html
COPYRIGHT and LICENSE
Here is the copyright information provided by Paul Schlyer:
Written as DAYLEN.C, 1989-08-16
Modified to SUNRISET.C, 1992-12-01
(c) Paul Schlyter, 1989, 1992
Released to the public domain by Paul Schlyter, December 1992
Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documentation files
(the "Software"), to deal in the Software without restriction,
including without limitation the rights to use, copy, modify, merge,
publish, distribute, sublicense, and/or sell copies of the Software,
and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:
The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
BUGS
SEE ALSO
perl(1).